Tissue injuries after an operation and the like evoke pain. Tissue injury leading to chronic pain is a field in which medicinal treatment effects are not well satisfied. The exact mechanisms of chronic pain still remain to be determined.
A variety of neurotransmitters are known to be involved in nociceptive modulation in the central nervous system, and research activities have been focused on such neurotransmitters. However, no magic bullets have not been established.
Recently, aminopropyl carbazole (P7C3) was discovered, and systematic administration of P7C3 has shown neuroprotective effects in animal models of neurodegenerative disease without knowledge of the clear action mechanisms. However, analgesic effects of P7C3 against pain have not been known.
Opioid is an analgesic, which usually acts on the receptors located in the central nervous system, and morphine is a representative drug of opioid.
Morphine exhibits affinity for the δ and κ opioid receptors, and is also active for the μ opioid receptors related to the central nervous system, brain, spinal cord, and thus exhibits effects such as pain alleviation, drowsiness, changes in mood, and mental clouding. Morphine belongs to a strong opioid class used for intermediate to severe pain. The opioids including morphine and morphine-like homologs have potent analgesic effects, but is reported to cause many side effects, for example, respiratory depression, nausea, vomiting, vertigo, clouding of consciousness, unpleasantness, pruritus, and constipation. Problems which aggravate biliary tract pressure, urinary tract retention, and hypotension symptoms have been reported. The development tolerance to opioid analgesia, the risks of drug dependency, the drug abuse, and the like are another undesirable effects. Therefore, studies on methods for decreasing the total amount of opioids used and obtaining synergistic effect for an analgesic action have continued.